Security Token Service

STS provides temporary credentials for AWS resource access
Users can use STS from sources, as
- Federation using Active Directory –
  - Requires SAML
  - temporary credentials as per user’s AD credentials
  - IAM user is not needed
  - With SSO, can also sign in to AWS console without any IAM credentials
- Federation of Mobile Apps with web federation
  - Web federation from Facebook/Amazon/Google/other OpenID providers
- Cross Account Access:
  - Users from one AWS account access to access resources in other one
Important terms
- Federation –join users in one domain with another like AD -> IAM
- Identity Broker – service to join or federate, identity from Domain A to Domain B
- Identity Store – Services storing identities like AD, Facebook, Google, Amazon, etc.
- Identities – user of service
Steps of Authentication
- User enters username/password
- Application calls an Identity Broker with username/password
- Identity Broker validate user identity with organizational centralized authentication like AD
- After validation, Identity Broker calls GetFederationToken function with IAM credentials covering IAM policy, permission and duration
- STS if called by user, returns following values
  - Access Key
  - Secret Access Key
  - Token
  - Duration of token
- Identity Broker sends temporary credentials to application
- Application sends requests to AWS using temporary credentials
- AWS verifies credentials by IAM and provide requested operation or service